From: Jason Merrill <jason@redhat.com>
To: gcc-patches@gcc.gnu.org
Subject: [pushed] c++: const void* memchr [PR113706]
Date: Wed, 1 May 2024 11:38:17 -0400 [thread overview]
Message-ID: <20240501154358.519660-1-jason@redhat.com> (raw)
Tested x86_64-pc-linux-gnu, applying to trunk.
-- 8< --
The C++ standard specifies that the <string.h> functions have const and
non-const overloads, unlike C's single function with const argument and
non-const return. Many systems don't actually implement this, but only add
an overload with non-const argument, so both end up having non-const return.
Solaris <string.h> does what the standard says, but we were penalizing it by
not recognizing the const overload as the built-in memchr.
PR c++/113706
gcc/cp/ChangeLog:
* decl.cc (decls_match): Handle memchr return type being
const-qualified.
gcc/testsuite/ChangeLog:
* g++.dg/opt/const-builtin1.C: New test.
* c-c++-common/pr103798-2.c: Remove xfail.
---
gcc/cp/decl.cc | 10 +++++++
gcc/testsuite/c-c++-common/pr103798-2.c | 3 +--
gcc/testsuite/g++.dg/opt/const-builtin1.C | 33 +++++++++++++++++++++++
3 files changed, 44 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/opt/const-builtin1.C
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index d88e0698652..df855334133 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -1156,6 +1156,16 @@ decls_match (tree newdecl, tree olddecl, bool record_versions /* = true */)
tree r2 = fndecl_declared_return_type (olddecl);
tree r1 = fndecl_declared_return_type (newdecl);
+ /* For memchr et al, allow const void* return type (as specified by C++)
+ when we expect void* (as in C). */
+ if (DECL_IS_UNDECLARED_BUILTIN (olddecl)
+ && DECL_EXTERN_C_P (olddecl)
+ && !same_type_p (r1, r2)
+ && TREE_CODE (r1) == POINTER_TYPE
+ && TREE_CODE (r2) == POINTER_TYPE
+ && comp_ptr_ttypes (TREE_TYPE (r1), TREE_TYPE (r2)))
+ r2 = r1;
+
tree p1 = TYPE_ARG_TYPES (f1);
tree p2 = TYPE_ARG_TYPES (f2);
diff --git a/gcc/testsuite/c-c++-common/pr103798-2.c b/gcc/testsuite/c-c++-common/pr103798-2.c
index 83cdfaa1660..e7e99c3679e 100644
--- a/gcc/testsuite/c-c++-common/pr103798-2.c
+++ b/gcc/testsuite/c-c++-common/pr103798-2.c
@@ -27,5 +27,4 @@ main ()
return 0;
}
-/* See PR c++/113706 for the xfail. */
-/* { dg-final { scan-assembler-not "memchr" { xfail { c++ && { *-*-solaris2* *-*-vxworks* } } } } } */
+/* { dg-final { scan-assembler-not "memchr" } } */
diff --git a/gcc/testsuite/g++.dg/opt/const-builtin1.C b/gcc/testsuite/g++.dg/opt/const-builtin1.C
new file mode 100644
index 00000000000..8b9987271c0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/const-builtin1.C
@@ -0,0 +1,33 @@
+// PR c++/113706
+/* A variant of the pr103798-2.c test with const void * memchr return type, as
+ specified by the C++ standard. */
+/* { dg-do run } */
+/* { dg-options "-O2 -fdump-tree-optimized -save-temps" } */
+
+extern "C" const void *memchr (const void *, int, __SIZE_TYPE__); // { dg-bogus "built-in" }
+
+__attribute__ ((weak))
+int
+f (int a)
+{
+ return memchr ("aE", a, 2) != 0;
+}
+
+__attribute__ ((weak))
+int
+g (char a)
+{
+ return a == 'a' || a == 'E';
+}
+
+int
+main ()
+{
+ for (int i = 0; i < 255; i++)
+ if (f (i + 256) != g (i + 256))
+ __builtin_abort ();
+
+ return 0;
+}
+
+/* { dg-final { scan-assembler-not "memchr" } } */
base-commit: c60b3e211c555706cdc2dc8bfcdd540152cff350
--
2.44.0
reply other threads:[~2024-05-01 15:44 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240501154358.519660-1-jason@redhat.com \
--to=jason@redhat.com \
--cc=gcc-patches@gcc.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).